Dual Inline Memory Modules (DIMMs) in various forms are used to provide memory expansion in a host computer. A DIMM typically includes a printed circuit board (PCB) with memory devices, such as DRAM or SDRAM, and supporting devices, such as ASICs, mounted to one or both sides. The DIMM is typically mounted in the host computer system by inserting a contact-bearing edge of the DIMM into a card edge connector on the host computer motherboard. This connection allows the host chipset, e.g., memory controller, to interface the DIMM.
Unregistered/unbuffered DIMMs do not include register components positioned between the memory devices and the host memory controller. Instead, the address and control signals from the memory controller are sent directly to every memory device on the DIMM. Unregistered/unbuffered DIMMs can be implemented in systems, such as personal computers, where scalability is of a lesser concern.
Registered DIMMs, sometimes referred to as buffered DIMMs, include additional register components, e.g., ASICS, positioned between the memory devices and the host memory controller. The register components buffer the address and control signals from the host memory controller, which helps reduce the loading and timing constraints of the host memory controller. This can help improve the scalability and reliability of the host memory.
Fully-Buffered Dual Inline Memory Module (FB-DIMM) technology is a relatively new memory architecture designed to allow for memory capacity growth commensurate with processor and I/O improvements. FB-DIMM technology replaces the traditional direct signaling interface between the host memory controller and the DRAM on the DIMM with two independent signaling interfaces—a parallel interface with the DRAM and a point-to-point serialized interface with the host memory controller. The FB-DIMM technology utilizes an advanced memory buffer (AMB) that provides a direct signaling interface between the serialized interface of the memory controller and the parallel interface of the DRAM.
The AMB interfaces with the memory controller and with DRAM ICs on the FB-DIMM to provide a parallel data stream to the DRAM ICs and a serialized data stream to the memory controller and other FB-DIMMs on the memory channel. In doing so, the AMBs utilize serialization/de-serialization (SerDes) technology to de-serialize the serialized data stream of the memory controller and serialize the parallel data stream of the DRAM ICs. The AMBs can support industry standards for the parallel interface with the DRAM ICs, such as double data rate (DDR), DDR2, and DDR3.